1. Field of the Invention
The present invention relates to a lens position adjusting apparatus, a lens position adjusting method and computer-readable medium. More particularly, the present invention relates to a lens position adjusting apparatus, a lens position adjusting method and computer-readable medium based on auto-focusing (hereinafter, referred to as AF) processing using a focus evaluation parameter.
2. Description of the Related Art
Contrast-based auto-focusing has been conventionally cited as a representative AF processing. This method extracts a high frequency component from image data picked up at individual lens positions using a high path filter (hereinafter, referred to as HPF) while moving a focus lens, thereby sequentially calculating a focus evaluation parameter, and then moves the focus lens to a lens position at which the evaluation focus parameter reaches the peak.
In addition, recently, an art to increase accuracy of AF has emerged by setting a cut-off frequency to be inputted to the HPF higher than ordinary cases, in the case where the AF processing is to be performed under a dark photography environment in which a spot light source is present, such as night photography.
This method is described for example in Japanese Laid-Open (Kokai) Patent Publication No. 11-88760 (1999).
Specifically, this method splits an image which has been picked up into a plurality of areas, integrates luminous signals in the plurality of areas, and compares the integrated value of the luminous signals in the plurality of areas with a reference value which has been set in advance. The camera judges that the photographing is conducted under a dark environment and switches to an HPF with a high cut-off frequency, if the proportion of a number of areas in which the integrated value is smaller than the reference value to a total number of areas exceeds a certain proportion.